1. Technical Field of the Invention
The present invention relates to a solid-state imaging device in which a microlens for condensing light is provided above a light-receiving part, and particularly to a solid-state imaging device in which an optical waveguide is provided between a light receiving part and a microlens in order to efficiently guide light to the light-receiving part.
2. Description of the Related Art
An on-chip microlens is provided above a light-receiving part of a photodiode (photoelectric conversion device), and the film thickness of an intermediate layer between the photodiode and the microlens has been set so that the focal position thereof is located in the vicinity of the light-receiving part of the photodiode. However, as an increase in the number of pixels (improvement for higher pixel number) is advanced, the size of each pixel is reduced, and accordingly, an alignment shift between the aperture of the pixel and the microlens, or an optical path shift at a small F value (when the diaphragm is opened) has a significant influence on the sensitivity of the light-receiving part.
In the related art disclosed in JP-A-7-45805, JP-A-8-139300, and JP-A-2002-118245, an optical waveguide is provided between a planarizing layer provided below a microlens and a photodiode. Setting is made such that the focal position of incident light passing through the microlens is in the vicinity of an interface (light incidence plane of an optical waveguide) between the planarizing layer and the optical waveguide, and light is efficiently guided to the photodiode by the optical waveguide.
It is disclosed that consequently, the above problem is solved, and it becomes possible to design the microlens having a high degree of freedom and the planarizing layer.
However, in the above related art, since the microlens and the optical waveguide are provided to be spaced from each other through the planarizing layer, a loss occurs in the light incident on the light-receiving part, and there is a fear that the sensitivity is lowered. Besides, since the microlens is formed of a resin having a low refractive index, in the case where an imaging device is sealed, it is necessary to provide a space above the microlens, and besides, since glass is generally used for sealing, there is a problem that the thickness can not be reduced and the cost becomes high.
Besides, since the planarizing layer is provided between the microlens and the optical waveguide, there is a problem that in the case where materials of the microlens, the planarizing layer, and the optical waveguide are different from one another, manufacturing must be made such that the incident light is not scattered at the respective interfaces.